There are many mobile or cellular network operators, or providers, in the world, often more than one in a single country. These network operators include, but are not limited to, operators who provide mobility services using GSM, GPRS, 3G, CDMA, TDMA, PHS, WCDMA, IDEN and WLL technology or their variants. These network operators provide voice and data services to their own subscribers and to subscribers from other networks. When the network operator provides service to a subscriber from a foreign country, it is referred to as “international roaming”. When the network operator provides service to a subscriber from another network in the same country, it is referred to as “domestic roaming”.
When the subscriber is registered in the network with which it has a direct billing relationship, the serving network is often referred to as the Home Public Mobile Network or HPMN. If the subscriber is in a network with which it does not have a direct billing relationship, the serving network is referred to as the Visited Public Mobile Network or VPMN, and the subscriber is referred to as an in-roamer by the VPMN. The same subscriber is referred to as an out-roamer by the HPMN. In such a case, the in-roamers are treated as temporary subscribers from a service availability perspective, while the billing for usage incurred by them is through inter-carrier settlements via the home network of the subscriber.
Various network operators have partnership agreements with each other that include more favorable roaming charges than non-partners receive. Partner networks are “preferred” networks for the network operator's subscriber to register with when roaming. Non-partner networks are “non-preferred” networks to the subscriber. Network operators can maximize their margins and the roamers can get more attractive roaming rates and services if roamers roam on their home mobile operator's preferred partner networks.
When “home” subscribers roam into visited networks, they may roam onto one, two or more VPMNs, any one at a time, based on various criteria. To better understand this, consider the cases when the handset can be in one of two modes: automatic network selection mode; or manual network selection mode.
In automatic mode, the handset automatically uses a set of rules to find the network to register with. The order of these rules may be handset vendor dependent; however, industry specifications state the order as:
1. The home network if it is available (based on MCC and MNC from IMSI); the list of networks from the Preferred PLMN List (EFPLMNSEL on SIM card) in priority order excluding the previously selected PLMN (the handset scans the GSM 900 frequency band before it scans the GSM 1800 frequency band);
4. Other PLMN with a received signal level above −85 dBm in random order excluding the previously selected PLMN; and
5. Any other PLMN excluding the previously selected PLMN in order of decreasing signal strength or alternatively the previously selected PLMN may be chosen ignoring its signal strength.
In manual mode, the handset shows a list of available networks to the user. The user selects one of them and the handset attempts registration onto that network. If the registration is not successful, the handset shows the list of networks to the user once again. In manual mode, the user has selected a particular network, so preferred VPMN selection from the HPMN perspective should not apply. However, a majority of current handsets are in automatic selection mode, and the HPMN is keen on controlling and/or influencing the roaming network chosen by its out-roamers. Also, since the HPMN would like to honor the manual selection mode, it has to identify the current settings on the handset. However, implementing a seamless mechanism to do this has been a challenge thus far.
Over the last few years, the revenues to network operators from home subscribers have consistently declined due to increased competition and resulting pricing pressures. On the other hand, revenues from roamers have consistently grown in the same period due to increased mobile penetration in local markets and an increase in travel. Moreover, roaming revenues are high-margin revenues that typically comprise between 8–25% of the total network operator revenues. Hence, protecting the existing roaming revenues and growing them further has become an important priority for the network operators worldwide.
Some operators also own networks in various countries. These operators would like to make sure their out-roamers stay within the group properties, or stay on preferred networks, in order to gain the best service experience even when roaming. They will also be able to offer geography based price plans (for example, a single rate all across Western Europe or South East Asia) to users who have subscribed to such plans. In addition, as new technologies keep rolling out, operators can control the rollout schedule across their own properties and also make sure interoperability issues are taken care of. Keeping roaming subscribers on preferred networks gives the best service experience to the subscriber. However, current methods of controlling which network a subscriber registers on when roaming have disadvantages.
For example, a commonly-used method of attempting to prevent roaming subscribers from registering with non-preferred networks includes storing a list of preferred networks on a SIM in the subscriber's handset (a Preferred PLMN list). The list can be burned on the SIM or updated using Over-The-Air (OTA) messages. This list influences the initial selection of the preferred network. However, due to various reasons (for example, the preferred network is not currently available or there is a temporary loss of coverage), the handset may also select a non-preferred network. The existing approach cannot control this situation and hence once the user is on a non-preferred network, he/she will remain there unless the non-preferred network loses the radio coverage. Even when the handset is powered off, the non-preferred network stays on the SIM card and on next power on it will be selected according to rules described herein. Thus, once the handset initiates an attempt to register on a non-preferred network, the network operator loses control of the roamer.
It would be advantageous for the network operator to retain some control over a roaming subscriber handset even when a handset has initiated a registration attempt with a non-preferred network for any reason, such as failure of the SIM network list to produce registration on a preferred network.